Process for manufacturing tetrafluoropropene

ABSTRACT

A process for manufacturing tetrafluoropropene, including, alternately: at least one step of reacting a chlorinated compound with hydrofluoric acid in the gas phase, in the presence of a fluorination catalyst, the proportion of oxygen optionally present being less than 0.05 mol. % relative to the chlorinated compound; a step of regenerating the fluorination catalyst by bringing the fluorination catalyst into contact with a regeneration stream including an oxidizing agent. Also, equipment suitable for carrying out this process.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.15/321,462, filed on Dec. 22, 2016, which is a U.S. national stage ofInternational Application No. PCT/FR2015/051653, filed on Jun. 22, 2015,which claims the benefit of French Application No. 1456303, filed onJul. 2, 2014. The entire contents of each of U.S. application Ser. No.15/321,462, International Application No. PCT/FR2015/051653, and FrenchApplication No. 1456303 are hereby incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a process for the manufacture oftetrafluoropropene (HFO-1234) and in particular of2,3,3,3-tetrafluoropropene (HFO-1234yf), and also to a plant suitablefor the implementation of this process.

TECHNICAL BACKGROUND

Greenhouse gases are gaseous components which absorb the infraredradiation emitted by the surface of the earth, thus contributing to thegreenhouse effect. The increase in their concentration in the atmosphereis one of the factors causing global warming.

The production of the chlorofluorocarbons (CFCs) andhydrochlorofluorocarbons (HCFCs) used in refrigeration and airconditioning systems has thus been successively regulated by theMontreal protocol and then the Kyoto protocol. There exists a need todevelop new molecules which are as effective and which in particularexhibit the smallest possible global warming potential. This is the casewith hydrofluoroolefins and in particular HFO-1234yf, which is aparticularly useful compound.

It is known to produce hydrofluoroolefins or hydrofluorocarbons byfluorination of hydrochloroolefins or of hydrochlorocarbons inparticular. This fluorination is generally a catalytic fluorinationusing hydrofluoric acid as fluorinating agent.

The fluorination reaction generally has to be carried out at a hightemperature (more than 300° C.) in the gas phase, in the presence of asupported or bulk solid catalyst.

It is known to provide cofeeding with an oxidizing agent, in particularair, or optionally chlorine, in order to preserve the lifetime of thecatalyst and to limit the deposition of coke at its surface during thereaction stage.

The document U.S. Pat. No. 8,614,361 describes a process for themanufacture of HFO-1234yf by reacting HCFO-1233xf with HF in thepresence of a high oxygen content.

The document U.S. Pat. No. 8,618,338 describes a process for themanufacture of fluoroolefin in two stages, in particular a first stageof reaction in the liquid phase starting from 1,1,2,3-tetrachloropropene(HCO-1230xa), in order to obtain the intermediate HCFO-1233xf, and asecond stage of reaction in the gas phase starting from HCFO-1233xf, inorder to obtain HFO-1234yf.

The document WO 2013/088195 teaches a process for the manufacture ofHFO-1234yf in two stages, a first stage of fluorination in the gas phaseof 1,1,1,2,3-pentachloropropane (HCC-240db) and/or of1,1,2,2,3-pentachloropropane (HCC-240aa), in order to obtain theintermediate HCFO-1233xf, and then a second stage of reaction in the gasphase starting from HCFO-1233xf, in order to obtain HFO-1234yf.

The documents WO 2012/098421 and WO 2012/098422 teach the activation andthe regeneration of fluorination catalysts.

The document WO 2013/182816 describes a chemical reaction process forthe alternating implementation of a phase of catalytic reaction and of aphase of regeneration of catalyst in a reactor.

There still exists a need to improve the processes for the manufactureof HFO-1234 compounds, such as HFO-1234yf, and in particular to producethese compounds with a high yield and with a high degree of purity.

SUMMARY

The invention relates first to a process for the manufacture oftetrafluoropropene, comprising, alternately:

-   -   at least one stage of reaction of a chlorinated compound with        hydrofluoric acid in the gas phase, in the presence of a        fluorination catalyst, the proportion of oxygen optionally        present being less than 0.05 mol % with respect to the        chlorinated compound;    -   a stage of regeneration of the fluorination catalyst by bringing        the fluorination catalyst into contact with a regeneration        stream comprising an oxidizing agent.

According to one embodiment, the stage of reaction of the chlorinatedcompound with hydrofluoric acid is carried out essentially in theabsence of oxygen and preferably essentially in the absence of anyoxidizing agent.

According to one embodiment, the regeneration stream contains at least 1mol % of oxygen with respect to the total regeneration stream.

According to one embodiment, the stage of reaction of the chlorinatedcompound with hydrofluoric acid is carried out in a single reactor,separately in time with respect to the stage of regeneration of thefluorination catalyst.

According to one embodiment, the stage of reaction of the chlorinatedcompound with hydrofluoric acid is carried out in at least one firstreactor, simultaneously with the implementation of the stage ofregeneration of the fluorination catalyst in at least one secondreactor.

According to one embodiment, the tetrafluoropropene is2,3,3,3-tetrafluoropropene.

According to one embodiment, the tetrafluoropropene is1,3,3,3-tetrafluoropropene.

According to one embodiment, the chlorinated compound is chosen fromtetrachloropropenes, chlorotrifluoropropenes, pentachloropropanes andmixtures of these.

According to one embodiment, the chlorinated compound is2-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is2,3,3,3-tetrafluoropropene.

According to one embodiment, the chlorinated compound is1,1,1,2,3-pentachloropropane and/or 1,1,2,2,3-pentachloropropane and thetetrafluoropropene is 2,3,3,3-tetrafluoropropene.

According to one embodiment, the chlorinated compound is1-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is1,3,3,3-tetrafluoropropene.

According to one embodiment, the process comprises:

-   -   a preliminary stage of manufacture of the chlorinated compound,        which is preferably a preliminary stage of reaction of a        preliminary compound with hydrofluoric acid in the gas phase, in        the presence of a preliminary fluorination catalyst, the        proportion of oxygen optionally present being less than 0.05 mol        % with respect to the preliminary compound.

According to one embodiment, the preliminary stage of reaction iscarried out alternately with:

-   -   a stage of regeneration of the preliminary fluorination catalyst        by bringing the preliminary fluorination catalyst into contact        with a regeneration stream comprising an oxidizing agent.

According to one embodiment, the preliminary compound is1,1,1,2,3-pentachloropropane and/or 1,1,2,2,3-pentachloropropane, thechlorinated compound is 1-chloro-3,3,3-trifluoropropene and thetetrafluoropropene is 2,3,3,3-tetrafluoropropene.

According to one embodiment, the process comprises:

-   -   the collecting of a stream of products on conclusion of the        preliminary reaction stage;    -   the separation of the stream of products into a first stream        comprising hydrochloric acid and tetrafluoropropene and a second        stream comprising hydrofluoric acid and the chlorinated        compound;    -   the use of said second stream to carry out the stage of reaction        of the chlorinated compound with hydrofluoric acid; and    -   optionally, the collecting of a stream of products on conclusion        of the stage of reaction of the chlorinated compound with        hydrofluoric acid and the recycling of the latter in the        preliminary reaction stage.

The invention also relates to a plant for the manufacture oftetrafluoropropene, comprising at least one gas-phase fluorinationreactor comprising a bed of fluorination catalyst, said gas-phasefluorination reactor being configured in order to be fed alternately by:

-   -   a system for feeding with reaction stream comprising a        chlorinated compound and hydrofluoric acid, the proportion of        oxygen optionally present in this reaction stream being less        than 0.05 mol % with respect to the chlorinated compound; and    -   a system for feeding with regeneration stream comprising an        oxidizing agent.

According to one embodiment, the reaction stream is essentially devoidof oxygen and preferably of any oxidizing agent.

According to one embodiment, the regeneration stream contains at least 1mol % of oxygen with respect to the total regeneration stream.

According to one embodiment, the plant comprises a single reactorconfigured in order to be fed alternately by the system for feeding withreaction stream and the system for feeding with regeneration stream.

According to one embodiment, the plant comprises a plurality ofreactors, each being configured in order to be fed alternately by asystem for feeding with reaction stream and a system for feeding withregeneration stream.

According to one embodiment, the plant is configured so that, when areactor is fed by the system for feeding with reaction stream, anotherreactor is fed by the system for feeding with regeneration stream.

According to one embodiment, the plant is configured so that:

-   -   the system for feeding with reaction stream feeds the reactor at        the bottom and the system for feeding with regeneration stream        feeds the reactor at the bottom; or    -   the system for feeding with reaction stream feeds the reactor at        the bottom and the system for feeding with regeneration stream        feeds the reactor at the top; or    -   the system for feeding with reaction stream feeds the reactor at        the top and the system for feeding with regeneration stream        feeds the reactor at the bottom; or    -   the system for feeding with reaction stream feeds the reactor at        the top and the system for feeding with regeneration stream        feeds the reactor at the top.

According to one embodiment:

-   -   the tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or    -   the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.

According to one embodiment, the chlorinated compound is chosen fromtetrachloropropenes, chlorotrifluoropropenes, pentachloropropanes andmixtures of these; and preferably:

-   -   the chlorinated compound is 2-chloro-3,3,3-trifluoropropene and        the tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or    -   the chlorinated compound is 1,1,1,2,3-pentachloropropane and/or        1,1,2,2,3-pentachloropropane and the tetrafluoropropene is        2,3,3,3-tetrafluoropropene; or    -   the chlorinated compound is 1-chloro-3,3,3-trifluoropropene and        the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.

According to one embodiment, the plant comprises:

-   -   at least one unit for the manufacture of chlorinated compound,        which preferably is at least one preliminary fluorination        reactor; configured in order to be fed by:    -   a system for feeding with reaction medium comprising a        preliminary compound and hydrofluoric acid, the proportion of        oxygen optionally present in this reaction stream being less        than 0.05 mol % with respect to the preliminary compound.

According to one embodiment, the preliminary fluorination reactor isalso configured in order to be fed by a system for feeding withregeneration stream comprising an oxidizing agent.

According to one embodiment, the preliminary compound is1,1,1,2,3-pentachloropropane and/or 1,1,2,2,3-pentachloropropane, thechlorinated compound is 1-chloro-3,3,3-trifluoropropene and thetetrafluoropropene is 2,3,3,3-tetrafluoropropene.

According to one embodiment, the plant comprises:

-   -   at least one first catalytic fluorination reactor;    -   at least one second catalytic fluorination reactor;    -   a system for collecting a stream of products connected at the        outlet of the first catalytic fluorination reactor;    -   a separation unit fed by the system for collecting a stream of        products;    -   a first collecting pipe and a second collecting pipe which are        connected at the outlet of the separation unit, the first        collecting pipe being configured in order to transport a stream        comprising hydrochloric acid and tetrafluoropropene and the        second collecting pipe being configured in order to transport a        stream comprising hydrofluoric acid and chlorinated compound;    -   an intermediate collecting system connected at the outlet of the        second reactor;    -   a first system for feeding with reaction medium configured in        order to feed the first reactor, this being itself fed by the        intermediate collecting system;    -   a second system for feeding with reaction medium configured in        order to feed the second reactor, this being itself fed by the        second collecting pipe;    -   a system for feeding with regeneration stream configured in        order to feed the first reactor and/or the second reactor; and    -   a system for collecting a stream of gases resulting from the        regeneration.

According to one embodiment, the plant comprises at least two secondreactors configured so that, when one of these reactors is fed by thesecond system for feeding with reaction stream, the other reactor is fedby the system for feeding with regeneration stream.

According to one embodiment, the plant comprises at least two firstreactors and two second reactors configured so that, when one of thefirst reactors and one of the second reactors are respectively fed bythe first system for feeding with reaction stream and the second systemfor feeding with reaction stream, the other first reactor and the othersecond reactor are fed by the system for feeding with regenerationstream; and which, preferably, is configured so that one and the sameregeneration stream resulting from the system for feeding withregeneration stream passes successively into the first reactor and thenthe second reactor or passes successively into the second reactor andthen the first reactor.

According to one embodiment, the plant comprises a single second reactorconfigured in order to be fed sequentially either by the second systemfor feeding with reaction stream or by the system for feeding withregeneration stream.

According to one embodiment, the plant comprises a single first reactorand a single second reactor configured in order to be fed sequentiallyeither by the second system for feeding with reaction stream or by thesystem for feeding with regeneration stream; and which, preferably, isconfigured so that one and the same regeneration stream resulting fromthe system for feeding with regeneration stream passes successively intothe first reactor and then the second reactor or passes successivelyinto the second reactor and then the first reactor.

The invention also relates to a composition comprisingtetrafluoropropene and containing, in molar proportions:

-   -   less than 100 ppm of chloromethane; and/or    -   less than 100 ppm of 1,1-difluoroethane; and/or    -   less than 100 ppm of fluoromethane; and/or    -   less than 100 ppm of difluoromethane.

According to one embodiment, the tetrafluoropropene is2,3,3,3-tetrafluoropropene.

According to one embodiment, the composition contains, in molarproportions:

-   -   less than 50 ppm of chloromethane; and/or    -   less than 50 ppm of 1,1-difluoroethane; and/or    -   less than 50 ppm of fluoromethane; and/or    -   less than 50 ppm of difluoromethane.

The present invention makes it possible to overcome the disadvantages ofthe state of the art. It more particularly provides a process for themanufacture of HFO-1234 (and in particular of HFO-1234yf) which has ahigh yield and which provides the desired product in a high degree ofpurity.

This is accomplished by virtue of the discovery, by the presentinventors, that some fluorination reaction stages can be carried outessentially in the absence of oxidizing agent, such as oxygen, withoutthe lifetime of the fluorination catalyst being visibly affected over apredetermined period, so long as intermediate regeneration stages areprovided.

An advantage resulting therefrom is that a gaseous stream of HFO-1234 ofa higher purity is obtained as it is obtained essentially in the absenceof oxygen during the reaction. The content of carbon oxides and also ofcompounds containing one or two carbons is markedly reduced with respectto the state of the art. The downstream treatment and the finalpurification of the desired product are thus simplified, guaranteeingthat the final product is obtained preferably with a purity of greaterthan or equal to 98%, advantageously of greater than or equal to 99% andvery advantageously of greater than or equal to 99.8% by weight. Thehydrochloric acid coproduced is also more easily recovered in value.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1a and 1b diagrammatically represent an embodiment of a plantaccording to the invention with just one catalytic fluorination reactor,in two different operating configurations.

FIGS. 2a and 2b diagrammatically represent an embodiment of a plantaccording to the invention with two catalytic fluorination reactors, intwo different operating configurations.

FIG. 3 diagrammatically represents an embodiment of a plant according tothe invention with three catalytic fluorination reactors, in aparticular operating configuration.

FIGS. 4a and 4b diagrammatically represent an embodiment of a plantaccording to the invention with just one catalytic fluorination reactor,in two different operating configurations.

FIGS. 5a and 5b diagrammatically represent an embodiment of a plantaccording to the invention with two catalytic fluorination reactors, intwo different operating configurations.

FIG. 6 diagrammatically represents an embodiment of a plant according tothe invention with three catalytic fluorination reactors, in aparticular operating configuration.

FIGS. 7 to 11 diagrammatically represent embodiments of plants accordingto the invention for the production of HFO-1234yf in two stages.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention is now described in more detail and without limitation inthe description which follows.

Unless otherwise mentioned, the percentages and proportions shown arevalues by weight.

The invention provides for the production of HFO-1234 by catalyticgas-phase fluorination; this catalytic fluorination is, according to theinvention, alternated with the regeneration of the fluorinationcatalyst. In some embodiments, the invention provides for the productionof HFO-1234 in several fluorination stages.

Fluorination Reaction for the Production of HFO-1234

The invention provides at least one fluorination stage, making itpossible to produce HFO-1234 from a chlorinated compound.

The HFO-1234 can in particular be HFO-1234yf or else HFO-1234ze(1,3,3,3-tetrafluoropropene), in the cis or trans form or in the form ofa mixture of cis and trans forms.

“Chlorinated compound” is understood to mean an organic compoundcomprising one or more chlorine atoms. This compound preferablycomprises three carbon atoms.

This chlorinated compound is preferably a propane or a propene havingsubstituents chosen from F, Cl, I and Br (preferably from F and Cl) andcomprising at least one Cl substituent.

It is understood that “chlorinated compound” is also understood to meanmixtures of compounds.

Preferably, the chlorinated compound is a tetrachloropropene, achlorotrifluoropropene, a pentachloropropane or a mixture of these.

In one embodiment, the chlorinated compound is2-chloro-3,3,3-trifluoropropene (HCFO-1233xf), in order to produceHFO-1234yf.

In another embodiment, the chlorinated compound is1-chloro-3,3,3-trifluoropropene (HCFO-1233zd), in order to produceHFO-1234ze.

In another embodiment, the chlorinated compound is1,1,1,2,3-pentachloropropane (HCC-240db) or 1,1,2,2,3-pentachloropropane(HCC-240aa), or a mixture of the two, in order to produce HFO-1234yf.

According to yet another embodiment, the chlorinated compound is2,3-dichloro-1,1,1-trifluoropropane (HCFC-243db), in order to produceHFO-1234yf.

According to yet another embodiment, the chlorinated compound is1,1,2,3-tetrachloropropene (HCO-1230xa) or 2,3,3,3-tetrachloropropene(HCO-1230xf) or a mixture of these two compounds, in order to produceHFO-1234yf.

The conversion of the chlorinated compound to give HFO-1234 can be adirect conversion or an indirect conversion (that is to say, involvingan intermediate product).

The fluorination of the chlorinated compound to give HFO-1234 is carriedout in one or more gas-phase fluorination reactors comprising a bed offluorination catalyst.

The catalyst used can, for example, be based on a metal comprising atransition metal oxide or a derivative or a halide or an oxyhalide ofsuch a metal. Mention may be made, for example, of FeCl₃, chromiumoxyfluoride, chromium oxides (optionally subjected to fluorinationtreatments), chromium fluorides and their mixtures. Other possiblecatalysts are catalysts supported on carbon, catalysts based on antimonyor catalysts based on aluminum (for example AlF₃ and Al₂O₃, aluminaoxyfluoride and alumina fluoride).

Use may be made, in general, of a chromium oxyfluoride, an aluminumfluoride, an aluminum oxyfluoride or a supported or unsupported catalystcontaining a metal, such as Cr, Ni, Fe, Zn, Ti, V, Zr, Mo, Ge, Sn, Pb,Mg or Sb.

Reference may be made, in this regard, to the document WO 2007/079431(on p. 7, I. 1-5 and 28-32), to the document EP 939071 (section [0022]),to the document WO 2008/054781 (on p. 9, I. 22-p. 10, I. 34) and to thedocument WO 2008/040969 (claim 1), to which documents reference isexpressly made.

The catalyst is more particularly preferably based on chromium and it ismore particularly a mixed catalyst comprising chromium.

According to one embodiment, a mixed catalyst comprising chromium andnickel is used. The Cr/Ni molar ratio (on the basis of the metalelement) is generally from 0.5 to 5, for example from 0.7 to 2, forexample approximately 1. The catalyst can contain from 0.5 to 20% byweight of chromium and from 0.5 to 20% by weight of nickel, preferablyfrom 2 to 10% of each.

The metal can be present in the metallic form or in the form of aderivative, for example an oxide, halide or oxyhalide. These derivativesare preferably obtained by activation of the catalytic metal.

The support preferably consists of aluminum, for example alumina,activated alumina or aluminum derivatives, such as aluminum halides andaluminum oxyhalides, for example described in the document U.S. Pat. No.4,902,838 or obtained by the activation process described above.

The catalyst can comprise chromium and nickel in an activated ornonactivated form, on a support which has or has not been subjected toactivation.

Reference may be made to the document WO 2009/118628 (in particular onp. 4, I. 30-p. 7, I. 16), to which reference is expressly made here.

Another preferred embodiment is based on a mixed catalyst containingchromium and at least one element chosen from Mg and Zn. The Mg or Zn/Cratomic ratio is preferably from 0.01 to 5.

Before its use, the catalyst is preferably subjected to activation withair, oxygen or chlorine and/or with HF.

For example, the catalyst is preferably subjected to activation with airor oxygen and HF at a temperature of 100 to 500° C., preferably of 250to 500° C. and more particularly of 300 to 400° C. The activation timeis preferably from 1 to 200 h and more particularly from 1 to 50 h.

This activation can be followed by a stage of final fluorinationactivation in the presence of an oxidizing agent, of HF and of organiccompounds.

The HF/organic compounds molar ratio is preferably from 2 to 40 and theoxidizing agent/organic compounds molar ratio is preferably from 0.04 to25. The temperature of the final activation is preferably from 300 to400° C. and its duration is preferably from 6 to 100 h.

The gas-phase fluorination reaction can be carried out:

-   -   with an HF/chlorinated compound molar ratio of 1:1 to 150:1,        preferably of 3:1 to 100:1 and more particularly preferably of        5:1 to 50:1;    -   with a contact time of 1 to 100 s, preferably 1 to 50 s and more        particularly 2 to 40 s (catalyst volume divided by the total        incoming stream, adjusted to the operating temperature and        pressure);    -   at an absolute pressure ranging from 0.1 to 50 bar, preferably        from 0.3 to 15 bar;    -   at a temperature (temperature of the catalyst bed) of 100 to        500° C., preferably of 200 to 450° C. and more particularly of        250 to 400° C.

The stream making up the reaction medium can comprise, in addition tothe HF and the chlorinated compound, additional compounds, in particularother halohydrocarbons or halohydroolefins.

The duration of the reaction stage is typically from 10 to 2000 hours,preferably from 50 to 500 hours and more particularly preferably from 70to 300 hours.

According to the invention, the proportion of oxygen optionally presentin the reaction medium is less than 0.05 mol % with respect to thechlorinated compound, more preferably less than 0.02 mol % or less than0.01 mol %. Traces of oxygen may possibly be present but thefluorination stage is preferably carried out essentially in the absenceof oxygen or in the complete absence of oxygen.

Preferably, the proportion of any oxidizing agent (such as oxygen andchlorine) optionally present in the reaction medium is less than 0.05mol % with respect to the chlorinated compound, more preferably lessthan 0.02 mol % or less than 0.01 mol %. Traces of oxidizing agent maypossibly be present, but the stage is preferably carried out essentiallyin the absence of oxidizing agent or in the complete absence ofoxidizing agent.

The stream of products resulting from the stage of fluorination of thechlorinated compound to give HFO-1234 can be subjected to appropriatetreatments (distillation, washing, etc.) in order to recover theHFO-1234 in the purified form and to separate it from the othercompounds present (HCl, unreacted HF, unreacted chlorinated compound,other organic compounds). One or more streams can be subject to arecycling.

The HCl in particular can be subject to a purification according to theprocess described in the application FR 13/61736, to which reference isexpressly made.

Regeneration of the Catalyst

In each reactor used for the implementation of the fluorination of thechlorinated compound to give HFO-1234, said fluorination can bealternated with phases of regeneration of the catalyst, in the presenceof oxygen.

It is possible, for example, to pass from the reaction phase to theregeneration phase when the conversion of the chlorinated compound fallsbelow a predetermined threshold, for example 50%.

If need be, beforehand, a transition period consisting in decompressingthe reaction gas phase is provided. It can be followed by a phase offlushing with an inert gas or else by placing under vacuum with the aimof completely removing the reactants present.

The regeneration stream preferably contains at least 1 mol % of oxygenin total. It can be pure air but the stream can also contain an inertgas of use in providing a degree of dilution, for example nitrogen,argon, helium or else hydrofluoric acid in proportions varying from 0 to95%, preferably from 5 to 85% and more particularly preferably from 10to 80%. The flow rate of the regeneration stream is preferably keptsufficiently high to prevent external diffusional conditions.

The temperature in the regeneration stage has a value, for example, from100 to 500° C., preferably from 200 to 450° C. and more particularlypreferably from 250 to 400° C. It may be practical to carry out theregeneration at the same temperature as the reaction.

The pressure in the regeneration stage has a value, for example, fromatmospheric pressure to 15 bar absolute. It is preferably approximatelyequal to atmospheric pressure.

The duration of the regeneration stage is typically from 10 to 2000hours, preferably from 50 to 500 hours and more particularly preferablyfrom 70 to 300 hours.

The regeneration can be carried out cocurrentwise or countercurrentwisewith respect to the direction of the stream used during the reactionperiod.

This regeneration stage makes it possible to recover the initialactivity of the catalyst. Several cycles can thus be linked togetherwithout significantly detrimentally affecting the activity of thecatalyst, which makes it possible to increase its lifetime.

On conclusion of the regeneration stage, the reactor can be placed undervacuum so as to remove the inert gases and the oxygen introduced, priorto the reintroduction of the organic compounds.

Plants According to the Invention for the Implementation of theFluorination Stage Described Above

The fluorination stage described above can be carried out with a singlereactor. In this case, the latter is operated alternately in reactionand in regeneration. Production is then noncontinuous.

Otherwise, the fluorination stage described above can be carried outwith a plurality of reactors, for example two, three or more than threereactors. In this case, it is possible to operate at least one reactorin reaction while at least one other is operated in regeneration, andthus optionally to provide continuous production.

Referring to FIGS. 1a and 1 b, an embodiment with just one reactor isdescribed.

The plant then comprises a reactor 10, capable of being fed either by asystem 2 a for feeding with reaction stream or by a system 2 b forfeeding with regeneration stream.

Both a system 3 a for collecting a stream of products and a system 3 bfor collecting a stream of gases resulting from the regeneration areconnected at the outlet of the reactor 10.

“System for feeding” and “system for collecting” are understood to meana single pipe or an assembly of several pipes.

A system 20 of valves at the inlet and a system 30 of valves at theoutlet are provided in order to make it possible to switch between therespective systems for feeding and for collecting.

During the reaction stage (FIG. 1a ), the system 20 of valves at theinlet is positioned in order for the reactor 10 to be fed by the system2 a for feeding with reaction stream, and the system 30 of valves at theoutlet is positioned in order for the reactor 10 to feed the system 3 afor collecting a stream of products, which directs the stream ofproducts toward units for the downstream treatment of the productiongases.

During the regeneration stage (FIG. 1b ), the system 20 of valves at theinlet is positioned in order for the reactor 10 to be fed by the system2 b for feeding with regeneration stream, and the system 30 of valves atthe outlet is positioned in order for the reactor 10 to feed the system3 b for collecting a stream of gases resulting from the regeneration,which directs the stream of gases resulting from the regenerationtowards units for the downstream treatment of these gases.

The reactor 10 alternately links together periods of production and ofregeneration sequentially. Production is noncontinuous.

Referring to FIGS. 2a and 2b , an embodiment with two reactors is nowdescribed. In a first configuration (FIG. 2a ), the reaction stage iscarried out in a first reactor 10 and the regeneration stage is carriedout in a second reactor 11. In a second configuration (FIG. 2b ), thereaction stage is carried out in the second reactor 11 and theregeneration stage is carried out in the first reactor 10. In this way,production is continuous.

Each reactor 10, 11 is provided with a system 20, 21 of valves at therespective inlet and also with a system 30, 31 of valves at therespective outlet in order to make it possible to pass from oneconfiguration to the other. It is possible to provide for the system 2 afor feeding with reaction stream, the system 2 b for feeding withregeneration stream, the system 3 a for collecting a stream of productsand the system 3 b for collecting a stream of gases resulting from theregeneration to be shared by the two reactors 10, 11, as illustrated, orelse to provide separate systems dedicated to each reactor 10, 11.Referring to FIG. 3, an embodiment with three reactors is now described.

In the configuration illustrated, the reaction stage is carried out in afirst reactor 10, a second reactor 11 is waiting and the regenerationstage is carried out in a third reactor 12. The waiting stage is a statein which the reactor has been regenerated and is ready to be used againin the reaction. In other non-illustrated configurations, the states ofthe reactors 10, 11, 12 are switched around. In this way, continuousproduction can be ensured.

Each reactor 10, 11, 12 is provided with a system 20, 21, 22 of valvesat the respective inlet and also with a system 30, 31, 32 of valves atthe respective outlet in order to make it possible to pass from oneconfiguration to the other. It is possible to provide for the system 2 afor feeding with reaction stream, the system 2 b for feeding withregeneration stream, the system 3 a for collecting a stream of productsand the system 3 b for collecting a stream of gases resulting from theregeneration to be shared by the three reactors 10, 11, 12 asillustrated or else to provide distinct systems dedicated to eachreactor 10, 11, 12.

In the embodiments of FIGS. 1 a, 1 b, 2 a, 2 b and 3, the streams in thereactors are oriented in the same direction for the fluorination and forthe regeneration.

According to alternative forms, the streams in the reactors can beoriented in reverse directions between the fluorination and theregeneration.

Thus, an embodiment is represented in FIGS. 4a and 4b with just onereactor 10 which is analogous to the embodiment of FIGS. 1a and 1 b,except that the streams are reversed between the fluorination and theregeneration. For example, if the system 2 a for feeding with reactionstream feeds the reactor 10 at the bottom, then the system 2 b forfeeding with regeneration stream feeds the reactor 10 at the top (orvice versa). Likewise, if the system 3 a for collecting a stream ofproducts is connected at the top of the reactor 10, then the system 3 bfor collecting a stream of gases resulting from the regeneration isconnected at the bottom of the reactor 10 (or vice versa).

Likewise, an embodiment is represented in FIGS. 5a and 5b with tworeactors 10, 11 which is analogous to the embodiment of FIGS. 2a and 2b, except that the streams are reversed between the fluorination and theregeneration. For example, if the system 2 a for feeding with reactionstream feeds the reactors 10, 11 at the bottom, then the system 2 b forfeeding with regeneration stream feeds the reactors 10, 11 at the top(or vice versa). Likewise, if the system 3 a for collecting a stream ofproducts is connected at the top of the reactors 10, 11, then the system3 b for collecting a stream of gases resulting from the regeneration isconnected at the bottom of the reactors 10, 11 (or vice versa).

Likewise, an embodiment is represented in FIG. 6 with three reactors 10,11, 12 which is analogous to the embodiment of FIG. 3, except that thestreams are reversed between the fluorination and the regeneration. Forexample, if the system 2 a for feeding with reaction stream feeds thereactors 10, 11, 12 at the bottom, then the system 2 b for feeding withregeneration stream feeds the reactors 10, 11, 12 at the top (or viceversa).

Likewise, if the system 3 a for collecting a stream of products isconnected at the top of the reactors 10, 11, 12, then the system 3 b forcollecting a stream of gases resulting from the regeneration isconnected at the bottom of reactors 10, 11, 12 (or vice versa).

Processes According to the Invention in Several Stages

In some embodiments, the invention provides several successive reactionstages and preferably: first a preliminary stage of the manufacture ofthe chlorinated compound mentioned above; then, subsequently, the stageof fluorination of the chlorinated compound to give HFO-1234.

Preferably, the preliminary stage is itself a fluorination stage.

In this case, this stage converts a preliminary compound into theabovementioned chlorinated compound. In such a case, it should be notedthat the chlorinated compound comprises at least one fluorine atom(since it results from a fluorination stage) and also at least onechlorine atom (since it is subsequently subjected to the fluorinationstage described above in order to provide HFO-1234).

The “preliminary compound” is advantageously an organic compound(preferably having three carbon atoms) which comprises at least twochlorine atoms (and which comprises more chlorine atoms than the“chlorinated compound”).

The preliminary compound can preferably be a propane or a propene havingsubstituents chosen from F, Cl, I and Br (preferably from F and Cl) andcomprising at least two Cl substituents. A propane is more particularlypreferred.

It is understood that “preliminary compound” is also understood to meanmixtures of compounds.

According to a preferred embodiment, the preliminary compound isHCC-240db or

HCC-240aa or a mixture of the two and the chlorinated compound isHCFO-1233xf, in order to produce HFO-1234yf.

According to yet another embodiment, the preliminary compound isHCFC-243db and the chlorinated compound is HCFO-1233xf, in order toproduce HFO-1234yf.

According to yet another embodiment, the preliminary compound isHCO-1230xa or HCO-1230xf or a mixture of these two compounds and thechlorinated compound is HCFO-1233xf, in order to produce HFO-1234yf.

The conversion of the preliminary compound into the chlorinated compoundcan be a direct conversion or an indirect conversion (that is to say,involving an intermediate product).

It is possible to carry out the fluorination of the preliminary compoundto give a chlorinated compound in the liquid phase. However, preferably,the fluorination is a gas-phase fluorination, in the presence of afluorination catalyst. It can be carried out in one or more fluorinationreactors in series or in parallel.

The fluorination catalyst can be of the same type as described above forthe fluorination of the chlorinated compound to give HFO-1234. The abovedescription relating to the activation of the catalyst also applies.

The reaction for the fluorination in the gas phase of the preliminarycompound to give a chlorinated compound can in particular be carriedout:

-   -   with an HF/organic compounds molar ratio of 3:1 to 100:1,        preferably of 5:1 to 50:1 (the term “organic compounds” denotes        all of the compounds of the reaction medium comprising one or        more carbon atoms);    -   at an absolute pressure ranging from 0.1 to 50 bar, preferably        from 0.3 to 15 bar;    -   with a contact time of 1 to 100 s, preferably of 1 to 50 s and        more particularly of 2 to 40 s (catalyst volume divided by the        total incoming stream, adjusted to the operating temperature and        pressure);    -   at temperature (temperature of the catalyst bed) of 100 to 500°        C., preferably of 200 to 450° C. and more particularly of 250 to        400° C.

The stream making up the reaction medium can comprise, in addition tothe HF and the preliminary compound, additional compounds, in particularother halohydrocarbons or halohydroolefins. The stream can, for example,already comprise an HFO-1234 fraction.

According to a preferred embodiment, there is no or essentially nooxygen (and optionally there is no or essentially no other oxidizingagent) in the reaction medium.

Thus, the presence of oxygen or of oxidizing agent in the subsequentfluorination stage is also avoided, without having to carry out anintermediate separation of a stream of oxygen or oxidizing agent.

The duration of the stage of reaction of the preliminary compound togive a chlorinated compound is typically from 10 to 2000 hours,preferably from 50 to 500 hours and more particularly preferably from 70to 300 hours.

On conclusion of this reaction stage, a stream of products is collectedwhich comprises in particular chlorinated compound, unreactedpreliminary compound, HF, HCl, optionally HFO-1234 and optionallysecondary products, such as in particular 1,1,1,2,2-pentafluoropropane(HFC-245cb).

This stream of products can subsequently directly feed the stage offluorination of the chlorinated compound to give HFO-1234yf describedabove.

Alternately, this stream of products can be separated, for example bydistillation, to provide, for example, a first stream comprising HCl andoptionally HFO-1234 and a second stream comprising HF and chlorinatedcompound. The distillation can, for example, be carried out at atemperature of −90 to 150° C., preferably of −85 to 100° C., and at apressure of 0.1 to 50 bar abs and preferably of 0.3 to 5 bar abs.

The first stream can be directed to a unit for the production of acid inorder to produce HCl and HFO-1234. The HFO-1234 and the intermediateproducts can be recovered by known means, such as extraction, washing,separation by settling and preferably distillation means.

It should be noted that, according to the invention, at least one of thetwo fluorination stages described above is alternated with a stage ofregeneration of the reactor or reactors with a stream of oxidizingagent, as described above in connection with the fluorination of thechlorinated compound to give HFO-1234. The above description thusapplies by analogy (including that relating to the different possibleplants illustrated in FIGS. 1a to 6):

-   -   either to the regeneration alternated with the fluorination of        the preliminary compound to give a chlorinated compound;    -   or to the regeneration alternated with the fluorination of the        chlorinated compound to give HFO-1234;    -   or both to the regeneration alternated with the fluorination of        the preliminary compound to give a chlorinated compound and to        the regeneration alternated with the fluorination of the        chlorinated compound to give HFO-1234.

Depending on the reaction conditions and the nature of the catalyst, thetendency of the catalyst to become deactivated can be different, hencethese various possible scenarios.

Processes for the Manufacture of HFO-1234yf in Two Stages

A description is now given of various embodiments in connection with themanufacture of HFO-1234yf in two stages starting from HCC-240db (itbeing understood that it is also possible instead to use HCC-240aa or amixture of the two): a first stage of conversion of HCC-240db to giveHCFO-1233xf and then a second stage of conversion of HCFO-1233xf to giveHFO-1234yf, which stages are carried out in successive reactors.

Referring to FIG. 7, according to one embodiment, a plant according tothe invention can thus comprise a first fluorination reactor 40 for theimplementation of the stage of preparation of HCFO-1233xf. It isunderstood that it is also possible instead to use a plurality ofreactors, operating in series and/or in parallel.

This first fluorination reactor 40 is fed by a first system 39 forfeeding with reaction medium (comprising HF and HCC-240db).

A system 41 for collecting a stream of products is positioned at theoutlet of the first fluorination reactor 40, which collecting systemfeeds a separation unit 42. This separation unit 42 can in particular bea distillation unit as described above.

A first collecting pipe 43 and a second collecting pipe 44 are providedat the outlet of the separation unit 42. The first collecting pipe 43 isconfigured in order to transport a stream comprising in particular HCland HFO-1234yf and the second collecting pipe 44 is configured in orderto transport a stream comprising in particular HF and HCFO-1233xf.

The first collecting pipe 43 feeds additional treatment units, notrepresented, which can in particular comprise a unit for the productionof acid, while the second collecting pipe 44 provides for recyclingtoward at least one second gas-phase fluorination reactor 48 which isused for the fluorination of HCFO-1233xf to give HFO-1234yf. This secondcollecting pipe 44 can thus also be described as a recycling pipe. Thissecond reactor 48 is fed by a second system 46 for feeding with reactionmedium, which itself is fed by the second collecting pipe 44, on the onehand, and by a system 45 for feeding with HF, on the other hand.

An intermediate collecting system 47 is connected at the outlet of thesecond reactor 48. This collecting system in turn feeds the first system39 for feeding with reaction medium of the first reactor 40. HCC-240dbis supplied by a system 38 for feeding with HCC-240db.

Preferably, in this plant and in all the fluorination stages, theproportion of oxygen optionally present in the streams is less than 0.05mol % with respect to the predominant organic compound, more preferablyless than 0.02 mol % or less than 0.01 mol %. Traces of oxygen maypossibly be present but, preferably, the whole of the process for thefluorination of HCC-240db to give HFO-1234yf is carried out essentiallyin the absence of oxygen or in the complete absence of oxygen.

Preferably, the proportion of any oxidizing agent (such as oxygen andchlorine) optionally present in the reaction medium is less than 0.05mol % with respect to the predominant organic compound, more preferablyless than 0.02 mol % or less than 0.01 mol %. Traces of oxidizing agentmay optionally be present but, preferably, the entire process for thefluorination of HCC-240db to give HFO-1234yf is carried out essentiallyin the absence of oxidizing agent or in the complete absence ofoxidizing agent.

In accordance with the invention, regeneration of the catalyst isprovided, alternating with the fluorination. This regeneration canconcern either the first reactor 40 or the second reactor 48 or both thereactors 40, 48. The regeneration is carried out as described above,using a stream of oxidizing agent. The means necessary for theregeneration are not represented in FIG. 7 but are analogous to thosedescribed above.

An alternative form is illustrated in FIG. 8. It is identical to theembodiment of FIG. 7 except that, instead of a single second reactor 48,two second reactors 48 a, 48 b are provided. These are configured tooperate alternately in fluorination mode and in regeneration mode, asdescribed above in connection with FIGS. 2a and 2 a.

Thus, by controlling a system 20, 21 of valves at the inlet and a system30, 31 of valves at the outlet, it is arranged that:

-   -   in one phase, one of the second reactors 48 a operates in        fluorination mode, that is to say is fed by the second system 46        for feeding with reaction medium and feeds the intermediate        collecting system 47, while the other of the second reactors 48        b operates in regeneration mode, that is to say is fed by a        system 49 for feeding with regeneration stream and itself feeds        a system 50 for collecting a stream of gases resulting from the        regeneration;    -   in another phase, the configurations of the two reactors 48 a,        48 b are reversed.

It should be noted that, in FIG. 8, a regeneration which is carried outin the same direction as the fluorination has been represented. However,the streams can also be reversed, as described in connection with FIGS.5a and 5 b.

Another alternative form is illustrated in FIG. 9. It is identical tothe embodiment of FIG. 8 except that not only are two second reactors 48a, 48 b provided but also two first reactors 40 a, 40 b are providedinstead of a single first reactor. These two first reactors areconfigured in order to operate alternately in fluorination mode and inregeneration mode, as described above in connection with FIGS. 2a and 2b.

In a first phase, which is that illustrated in the figure, the secondsystem 46 for feeding with reaction medium feeds one of the two secondreactors 48 a. The intermediate collecting system 47 is connected at theoutlet of this second reactor 48 a, which makes it possible to collect astream of intermediate products. This feeds the first system 39 forfeeding with reaction medium (also with the system 38 for feeding withHCC-240db), which itself feeds one of the two first reactors 40 a.

The system 41 for collecting a stream of products is connected at theoutlet of this first reactor 40 a.

The system 49 for feeding with regeneration stream feeds the othersecond reactor 48 b, preferably simultaneously. A system 52 for theintermediate collecting of a stream of gases resulting from theregeneration is connected at the outlet of this second reactor 48 b andfeeds, at the inlet, the other first reactor 40 b. The system 50 for theintermediate collecting of a stream of gases resulting from theregeneration is connected at the outlet of this first reactor 40 b.

Alternatively, intermediate feeding with an additional regenerationstream can be provided between the two reactors 48 b, 40 b.Alternatively again, regeneration by streams independent of these tworeactors 48 b, 40 b can be provided.

Alternately again, regeneration with streams in the reverse direction tothose of the fluorination can be provided, according to the principlesof FIGS. 5a and 5 b.

In a second phase, not illustrated, the fluorination and regenerationconfigurations are reversed between the reactors.

The change from one configuration to the other is provided by means ofan assembly of valves: in the example illustrated, the valves are valves20, 21 at the inlet 20, 21, which are located upstream of the secondreactors 48 a, 48 b, valves at the outlet, which are located downstreamof the first reactors 40 a, 40 b, and finally an HCC-240db valve 51located at the system 38 for feeding with HCC-240db.

Another alternative form is illustrated in FIG. 10. It is analogous tothe embodiment of FIG. 7. In this alternative form, sequentialregeneration with respect to the fluorination (and not simultaneousregeneration) is provided, on just one of the two reactors, namely thesecond reactor 48.

To this end, the system 49 for feeding with regeneration stream isconnected at the inlet of the second reactor 48 and the system 50 forcollecting a stream of gases resulting from the regeneration isconnected at the outlet of the second reactor 48. A system 20 of valvesat the inlet and a system 30 of valves at the outlet makes it possibleto switch the second reactor 48, either into fluorination mode or intoregeneration mode.

It should be noted that the fluorination and regeneration streams can bein the same direction or in the opposite direction.

It should also be noted that it is also possible to provide the samemeans for ensuring the regeneration at the first reactor 40, either inaddition to or as a replacement for the regeneration means of the secondreactor 48.

Another alternative form is illustrated in FIG. 11. It is analogous tothe embodiment of FIG. 7. In this alternative form, sequentialregeneration with respect to the fluorination (and not simultaneousregeneration) is provided, on the two reactors simultaneously, namelythe first reactor 40 and the second reactor 48.

To this end, the system 49 for feeding with regeneration stream isconnected at the inlet of the second reactor 48 and the system 50 forcollecting a stream of gases resulting from the regeneration isconnected at the outlet of the first reactor 40. A system 20 of valvesat the inlet and a system 30 of valves at the outlet makes it possibleto switch the reactors 40, 48, either into fluorination mode or intoregeneration mode.

It should be noted that the fluorination and regeneration streams can bein the same direction or in the opposite direction.

Everything which has been described here in connection with thepreparation of HFO-1234yf in two stages can be read analogously byreplacing HCC-240db with another starting preliminary compound (and byreplacing HCFO-1233xf with another chlorinated compound). Likewise, thatwhich has been described here can be applied analogously to thepreparation of other HFO-1234 compounds.

Another possibility for the implementation of the invention consists in:on the one hand, producing chlorinated compound from the preliminarycompound (for example HCFO-1233xf from HCC-240db or similar) and, on theother hand, producing HFO-1234 from chlorinated compound (for exampleHFO-1234yf from HCFO-1233xf), this being done independently andseparately, for example by isolating, storing and/or transporting thechlorinated compound between the two stages, and by carrying out thealternating regeneration according to the invention on the first stageor the second stage or both, independently.

Products Obtained

The consequence of the absence or virtual absence of oxygen during thereaction phase is the decrease in the content of impurities related tothe combustion or decomposition reactions of the molecules. Theimpurities are carbon oxides or dioxides and also the moleculescontaining fewer carbon atoms than the starting chlorinated product.

Thus, the invention makes it possible to obtain a stream of HFO-1234(and in particular of HFO-1234yf) containing less chloromethane (HCC-40)and 1,1-difluoroethane (HFC-152a) than in the state of the art. In pointof fact, these compounds form an azeotrope with HFO-1234yf, which makesthem difficult to purify.

The invention also makes it possible to obtain a stream of HFO-1234 (andin particular of HFO-1234yf) containing less fluoromethane (HFC-41) anddifluoromethane (HFC-32) than in the state of the art. In point of fact,it is known that these compounds are extremely flammable.

The molar proportion of each of these compounds in the HFO-1234 streamis thus preferably less than 100 ppm and more particularly less than 50ppm.

According to one embodiment, this stream contains HFO-1234 (preferablyHFO-1234yf) and also from 1 to 50 ppm of HCC-40, from 1 to 50 ppm ofHFC-152a, from 1 to 50 ppm of HFC-41 and from 1 to 50 ppm of HFC-32.

According to one embodiment, this stream is essentially devoid andpreferably is devoid of HCC-40.

According to one embodiment, this stream is essentially devoid andpreferably is devoid of HFC-152a.

According to one embodiment, this stream is essentially devoid andpreferably is devoid of HFC-41.

According to one embodiment, this stream is essentially devoid andpreferably is devoid of HFC-32.

According to one embodiment, this stream contains at least 98% ofHFO-1234, preferably at least 99% and in particular at least 99.5%,indeed even at least 99.8%, by weight.

The HFO-1234 stream under consideration is either the stream obtained atthe outlet of the reactor for the fluorination of the chlorinatedcompound to give HFO-1234 (stream withdrawn in the system 3 a forcollecting a stream of product in the figures), or the stream obtainedat the outlet of the separation unit (stream withdrawn in the firstcollecting pipe 43 in the figures), or the stream obtained later stillafter separation of the HFO-1234 and the hydrochloric acid.

Furthermore, the absence or virtual absence of oxygen also makes itpossible to obtain a stream of hydrochloric acid with a greater puritywhich makes possible easier recovery in value. Thus, the stream ofhydrochloric acid recovered after separation from HFO-1234 is preferablydevoid (or essentially devoid) of trifluoroacetic acid, of COF₂ or ofCOFCl.

EXAMPLES

The following examples illustrate the invention without limiting it.

A gas-phase fluorination reactor equipped with feeding with HF, withfeeding with fresh organic products, with available feeding for thecofeeding of another gaseous compound and with a pipe for feedingresulting from the recycling of the unconverted reactants is available.

The outflow of the gas stream resulting from this reactor is sent to apipe cooled with a jacket which makes it possible to cool and partiallycondense the reaction products before they are introduced into thedistillation column. The partially condensed stream is thus conveyed toa distillation column with a height of 1.5 m filled with a metal packingof Sulzer type which facilitates the exchanges between the ascending gasstream and the descending liquid reflux. The distillation column isequipped with a boiler at the column bottom and with a condensationsystem at the top. This separation unit makes it possible to separate atop stream which predominantly consists of the desired product(HFO-1234yf) and of the byproduct HCl. Greater or lesser amounts ofbyproduct HFC-245cb are also present. The column bottom streampredominantly consists of HF and of unconverted reactant (HCFO-1233xf)and also of the byproduct HFC-245cb resulting from the addition of HF toHFO-1234yf. This column bottom stream is subsequently recycled to thegas-phase reactor. Traces of impurities are present in each of thestreams.

180 ml of bulk chromium-based catalyst are introduced into the reactormade of Inconel. It is first subjected to a period of drying under 50l/h of nitrogen at atmospheric pressure at 275° C. overnight.Subsequently, while maintaining the nitrogen and still at 275° C., astream of HF is gradually added until a flow rate of 1 mol/h isobtained. This treatment is maintained overnight. The nitrogen issubsequently halted and the temperature of the oven is increased to 350°C. The treatment under pure HF is thus also maintained overnight.Finally, a treatment under 5 l/h of air is applied for at least 24 h.

Following the treatment for activation of the catalyst, the reactantsHCFO-1233xf and HF are introduced into the recycling loop so as to fillthis part of the plant while retaining a molar ratio of the hydrofluoricacid to the organic compound of 25. Initiation is carried out by feedingthe liquid present in the recycling loop to the gas-phase reactor (apreheater ensures the prior vaporization of the reactants). The systemsubsequently gradually becomes equilibrated between the unconvertedreactants, which are recycled, the products formed, which are dischargedfrom and collected outside the system, and the fresh reactants, whichare continuously fed so as to compensate exactly for the amount ofproducts discharged. The level of liquid in the distillation column thusremains constant.

The conversion of the catalyst changes over time and graduallydecreases. When the conversion falls below 50%, a regeneration treatmentwith air is applied to the catalyst. This treatment makes it possible tofully recover the initially activity of the catalyst.

The conversion is calculated from the molar content of HCFO-1233xfmeasured at the inlet of the reactor (sum of the recycling and freshorganic compound streams) and from the content of HCFO-1233xf measuredat the outlet of the reactor.

Example 1—Catalytic Results in the Presence of Air

A test is carried out under the following operating conditions: thecatalyst is freshly regenerated, the molar ratio of HF to the organiccompounds is 25, the gas-phase contact time is 15 seconds, thetemperature is 350° C. and 10 mol % of oxygen are added with respect tothe sum of the organic compounds introduced. The conversion of theHCFO-1233xf obtained over time is given in table 1 below. During thistest, the gas stream exiting from the top of the distillation column isanalyzed by gas chromatography. The analysis is given in table 2 below(value as % of GC area).

Example 2—Catalytic Results Without Air

The procedure of example 1 is taken up again but without addition ofsupplementary oxygen to the gas phase. The results obtained for theconversion over time are given in table 1 below. The analysis of the gasstream exiting from the distillation column is given in table 2 below(value as % of GC area). The carbon oxides and the C₁ and C₂ impuritiesare markedly reduced. The purity of the sum of the desired productHFO-1234yf and of the recyclable byproduct HFC-245cb increases.

TABLE 1 Example 1 Example 2 Conversion of Conversion of Time (h)HCFO-1233xf (%) Time (h) HCFO-1233xf (%) 4 78.6 15 77.6 8 77.4 19 78.512 76.3 24 77.8 16 77.2 27 78.3 21 78.7 31 76.9 28 76.2 35 74.5 32 76.839 72.8 36 76.9 43 71.7 40 75.9 48 72.7 48 75.6 51 72.9 52 73.4 55 73.260 73.4 59 73.6 64 72.1 63 74.1 71 70.2 71 70.9 80 67.8 82 70.9 84 65.086 69.4

TABLE 2 Product detected Example 1 Example 2 CO 3.2 0.22 CO₂ 1.39 0.04F23 0.13 Nd F41 0.06 Nd F32 0.03 Nd F125 0.17 Nd Trifluoropropyne 0.080.02 F143a 0.36 0.04 F1234yf + 245cb 93.19 98.03  F40 0.26 Nd F152a 0.02Nd F1234zeE 1.10 1.62 F1233xf 0.01 Nd Nd: not detected

Embodiments

-   1. A process for the manufacture of tetrafluoropropene, comprising,    alternately:    -   at least one stage of reaction of a chlorinated compound with        hydrofluoric acid in the gas phase, in the presence of a        fluorination catalyst, the proportion of oxygen optionally        present being less than 0.05 mol % with respect to the        chlorinated compound;    -   a stage of regeneration of the fluorination catalyst by bringing        the fluorination catalyst into contact with a regeneration        stream comprising an oxidizing agent.-   2. The process as in embodiment 1, in which the stage of reaction of    the chlorinated compound with hydrofluoric acid is carried out    essentially in the absence of oxygen and preferably essentially in    the absence of any oxidizing agent.-   3. The process as in embodiment 1 or 2, in which the regeneration    stream contains at least 1 mol % of oxygen with respect to the total    regeneration stream.-   4. The process as in one of embodiments 1 to 3, in which the stage    of reaction of the chlorinated compound with hydrofluoric acid is    carried out in a single reactor, separately in time with respect to    the stage of regeneration of the fluorination catalyst.-   5. The process as in one of embodiments 1 to 3, in which the stage    of reaction of the chlorinated compound with hydrofluoric acid is    carried out in at least one first reactor, simultaneously with the    implementation of the stage of regeneration of the fluorination    catalyst in at least one second reactor.-   6. The process as in one of embodiments 1 to 5, in which the    tetrafluoropropene is 2,3,3,3-tetrafluoropropene.-   7. The process as in one of embodiments 1 to 5, in which the    tetrafluoropropene is 1,3,3,3-tetrafluoropropene.-   8. The process as in one of embodiments 1 to 7, in which the    chlorinated compound is chosen from tetrachloropropenes,    chlorotrifluoropropenes, pentachloropropanes and mixtures of these.-   9. The process as in one of embodiments 1 to 6 and 8, in which the    chlorinated compound is 2-chloro-3,3,3-trifluoropropene and the    tetrafluoropropene is 2,3,3,3-tetrafluoropropene.-   10. The process as in one of embodiments 1 to 6 and 8, in which the    chlorinated compound is 1,1,1,2,3-pentachloropropane and/or    1,1,2,2,3-pentachloropropane and the tetrafluoropropene is    2,3,3,3-tetrafluoropropene.-   11. The process as in one of embodiments 1 to 5 and 7 and 8, in    which the chlorinated compound is 1-chloro-3,3,3-trifluoropropene    and the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.-   12. The process as in one of embodiments 1 to 11, comprising:    -   a preliminary stage of manufacture of the chlorinated compound,        which is preferably a preliminary stage of reaction of a        preliminary compound with hydrofluoric acid in the gas phase, in        the presence of a preliminary fluorination catalyst, the        proportion of oxygen optionally present being less than 0.05 mol        % with respect to the preliminary compound.-   13. The process as in embodiment 12, in which the preliminary stage    of reaction is carried out alternately with:    -   a stage of regeneration of the preliminary fluorination catalyst        by bringing the preliminary fluorination catalyst into contact        with a regeneration stream comprising an oxidizing agent.-   14. The process as in either of embodiments 12 and 13, in which the    preliminary compound is 1,1,1,2,3-pentachloropropane and/or    1,1,2,2,3-pentachloropropane, the chlorinated compound is    1-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is    2,3,3,3-tetrafluoropropene.-   15. The process as in one of embodiments 12 to 14, comprising:    -   the collecting of a stream of products on conclusion of the        preliminary reaction stage;    -   the separation of the stream of products into a first stream        comprising hydrochloric acid and tetrafluoropropene and a second        stream comprising hydrofluoric acid and the chlorinated        compound;    -   the use of said second stream to carry out the stage of reaction        of the chlorinated compound with hydrofluoric acid; and    -   optionally, the collecting of a stream of products on conclusion        of the stage of reaction of the chlorinated compound with        hydrofluoric acid and the recycling of the latter in the        preliminary reaction stage.-   16. A plant for the manufacture of tetrafluoropropene, comprising at    least one gas-phase fluorination reactor (10) comprising a bed of    fluorination catalyst, said gas-phase fluorination reactor (10)    being configured in order to be fed alternately by:    -   a system (2 a) for feeding with reaction stream (2 a) comprising        a chlorinated compound and hydrofluoric acid, the proportion of        oxygen optionally present in this reaction stream being less        than 0.05 mol % with respect to the chlorinated compound; and    -   a system (2b) for feeding with regeneration stream comprising an        oxidizing agent.-   17. The plant as in embodiment 16, in which the reaction stream is    essentially devoid of oxygen and preferably of any oxidizing agent.-   18. The plant as in embodiment 16 or 17, in which the regeneration    stream contains at least 1 mol % of oxygen with respect to the total    regeneration stream.-   19. The plant as in one of embodiments 16 to 18, comprising a single    reactor (10) configured in order to be fed alternately by the system    (2 a) for feeding with reaction stream and the system (2 b) for    feeding with regeneration stream.-   20. The plant as in one of embodiments 16 to 18, comprising a    plurality of reactors (10, 11, 12), each being configured in order    to be fed alternately by a system (2 a) for feeding with reaction    stream and a system (2 b) for feeding with regeneration stream.-   21. The plant as in embodiment 20, configured so that, when a    reactor (10) is fed by the system (2 a) for feeding with reaction    stream, another reactor (11) is fed by the system (2 b) for feeding    with regeneration stream.-   22. The plant as in one of embodiments 16 to 21, configured so that:    -   the system (2 a) for feeding with reaction stream feeds the        reactor (10) at the bottom and the system (2 b) for feeding with        regeneration stream feeds the reactor (10) at the bottom; or    -   the system (2 a) for feeding with reaction stream feeds the        reactor (10) at the bottom and the system (2 b) for feeding with        regeneration stream feeds the reactor (10) at the top; or    -   the system (2 a) for feeding with reaction stream feeds the        reactor (10) at the top and the system (2 b) for feeding with        regeneration stream feeds the reactor (10) at the bottom; or    -   the system (2 a) for feeding with reaction stream feeds the        reactor (10) at the top and the system (2 b) for feeding with        regeneration stream feeds the reactor (10) at the top.-   23. The plant as in one of embodiments 16 to 22, in which:    -   the tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or    -   the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.-   24. The plant as in one of embodiments 16 to 23, in which the    chlorinated compound is chosen from tetrachloropropenes,    chlorotrifluoropropenes, pentachloropropanes and mixtures of these;    and preferably:    -   the chlorinated compound is 2-chloro-3,3,3-trifluoropropene and        the tetrafluoropropene is 2,3,3,3-tetrafluoropropene; or    -   the chlorinated compound is 1,1,1,2,3-pentachloropropane and/or        1,1,2,2,3-pentachloropropane and the tetrafluoropropene is        2,3,3,3-tetrafluoropropene; or    -   the chlorinated compound is 1-chloro-3,3,3-trifluoropropene and        the tetrafluoropropene is 1,3,3,3-tetrafluoropropene.-   25. The plant as in one of embodiments 16 to 24, comprising:    -   at least one unit for the manufacture of chlorinated compound,        which preferably is at least one preliminary fluorination        reactor (40); configured in order to be fed by:    -   a system (39) for feeding with reaction medium comprising a        preliminary compound and hydrofluoric acid, the proportion of        oxygen optionally present in this reaction stream being less        than 0.05 mol % with respect to the preliminary compound.-   26. The plant as in embodiment 25, in which the preliminary    fluorination reactor (40) is also configured in order to be fed by a    system (49) for feeding with regeneration stream comprising an    oxidizing agent.-   27. The plant as in either of embodiments 25 and 26, in which the    preliminary compound is 1,1,1,2,3-pentachloropropane and/or    1,1,2,2,3-pentachloropropane, the chlorinated compound is    1-chloro-3,3,3-trifluoropropene and the tetrafluoropropene is    2,3,3,3-tetrafluoropropene.-   28. The plant as in one of embodiments 16 to 27, comprising:    -   at least one first catalytic fluorination reactor (40);    -   at least one second catalytic fluorination reactor (48);    -   a system (41) for collecting a stream of products connected at        the outlet of the first catalytic fluorination reactor (40);    -   a separation unit (42) fed by the system (41) for collecting a        stream of products;    -   a first collecting pipe (43) and a second collecting pipe (44)        which are connected at the outlet of the separation unit (42),        the first collecting pipe (43) being configured in order to        transport a stream comprising hydrochloric acid and        tetrafluoropropene and the second collecting pipe (44) being        configured in order to transport a stream comprising        hydrofluoric acid and chlorinated compound;    -   an intermediate collecting system (47) connected at the outlet        of the second reactor (48);    -   a first system (39) for feeding with reaction medium configured        in order to feed the first reactor (40), this being itself fed        by the intermediate collecting system (47);    -   a second system (46) for feeding with reaction medium configured        in order to feed the second reactor (48), this being itself fed        by the second collecting pipe (44);    -   a system (49) for feeding with regeneration stream configured in        order to feed the first reactor (40) and/or the second reactor        (48); and    -   a system (50) for collecting a stream of gases stream resulting        from the regeneration (50).-   29. The plant as in embodiment 28, which comprises at least two    second reactors (48 a, 48 b) configured so that, when one of these    reactors (48 a) is fed by the second system (46) for feeding with    reaction stream, the other reactor (48 b) is fed by the system (49)    for feeding with regeneration stream.-   30. The plant as in embodiment 28, which comprises at least two    first reactors (40 a, 40 b) and two second reactors (48 a, 48 b)    configured so that, when one of the first reactors (40 a) and one of    the second reactors (48 a) are respectively fed by the first system    (39) for feeding with reaction stream and the second system (46) for    feeding with reaction stream, the other first reactor (40 b) and the    other second reactor (48 b) are fed by the system (49) for feeding    with regeneration stream; and which, preferably, is configured so    that one and the same regeneration stream resulting from the system    (49) for feeding with regeneration stream passes successively into    the first reactor (40 b) and then the second reactor (48 b) or    passes successively into the second reactor (48 b) and then the    first reactor (40 b).-   31. The plant as in embodiment 28, which comprises a single second    reactor (48) configured in order to be fed sequentially either by    the second system (46) for feeding with reaction stream or by the    system (49) for feeding with regeneration stream.-   32. The plant as in embodiment 28, which comprises a single first    reactor (40) and a single second reactor (48), configured in order    to be fed sequentially either by the second system (46) for feeding    with reaction stream or by the system (49) for feeding with    regeneration stream; and which, preferably, is configured so that    one and the same regeneration stream resulting from the system (49)    for feeding with regeneration stream passes successively into the    first reactor (40) and then the second reactor (48) or passes    successively into the second reactor (48) and then the first reactor    (40).-   33. A composition comprising tetrafluoropropene and containing, in    molar proportions:    -   less than 100 ppm of chloromethane; and/or    -   less than 100 ppm of 1,1-difluoroethane; and/or    -   less than 100 ppm of fluoromethane; and/or    -   less than 100 ppm of difluoromethane.-   34. The composition as in embodiment 33, in which the    tetrafluoropropene is 2,3,3,3-tetrafluoropropene.-   35. The composition as in embodiment 33 or 34, containing, in molar    proportions:    -   less than 50 ppm of chloromethane; and/or    -   less than 50 ppm of 1,1-difluoroethane; and/or    -   less than 50 ppm of fluoromethane; and/or    -   less than 50 ppm of difluoromethane.

1. A plant for the manufacture of tetrafluoropropene, comprising atleast one gas-phase fluorination reactor comprising a bed offluorination catalyst, said gas-phase fluorination reactor beingconfigured in order to be fed alternately by: a system for feeding withreaction stream comprising a chlorinated compound and hydrofluoric acid,the proportion of oxygen optionally present in this reaction streambeing less than 0.05 mol % with respect to the chlorinated compound; anda system for feeding with regeneration stream comprising an oxidizingagent.
 2. The plant as claimed in claim 1, in which the reaction streamis essentially devoid of oxygen.
 3. The plant as claimed in claim 1, inwhich the regeneration stream contains at least 1 mol % of oxygen withrespect to the total regeneration stream.
 4. The plant as claimed inclaim 1, comprising a single reactor configured in order to be fedalternately by the system for feeding with reaction stream and thesystem for feeding with regeneration stream.
 5. The plant as claimed inclaim 1, comprising a plurality of reactors, each being configured inorder to be fed alternately by a system for feeding with reaction streamand a system for feeding with regeneration stream.
 6. The plant asclaimed in claim 5, configured so that, when a reactor is fed by thesystem for feeding with reaction stream, another reactor is fed by thesystem for feeding with regeneration stream.
 7. The plant as claimed inclaim 1, configured so that: the system for feeding with reaction streamfeeds the reactor at the bottom and the system for feeding withregeneration stream feeds the reactor at the bottom; or the system forfeeding with reaction stream feeds the reactor at the bottom and thesystem for feeding with regeneration stream feeds the reactor at thetop; or the system for feeding with reaction stream feeds the reactor atthe top and the system for feeding with regeneration stream feeds thereactor at the bottom; or the system for feeding with reaction streamfeeds the reactor at the top and the system for feeding withregeneration stream feeds the reactor at the top.
 8. The plant asclaimed in claim 1, in which: the tetrafluoropropene is2,3,3,3-tetrafluoropropene; or the tetrafluoropropene is1,3,3,3-tetrafluoropropene.
 9. The plant as claimed in claim 1, in whichthe chlorinated compound is chosen from tetrachloropropenes,chlorotrifluoropropenes, pentachloropropanes and mixtures of these. 10.The plant as claimed in claim 1, comprising: at least one unit for themanufacture of chlorinated compound; configured in order to be fed by: asystem for feeding with reaction medium comprising a preliminarycompound and hydrofluoric acid, the proportion of oxygen optionallypresent in this reaction stream being less than 0.05 mol % with respectto the preliminary compound.
 11. The plant as claimed in claim 10, inwhich the preliminary fluorination reactor is also configured in orderto be fed by a system for feeding with regeneration stream comprising anoxidizing agent.
 12. The plant as claimed in claim 10, in which thepreliminary compound is 1,1,1,2,3-pentachloropropane and/or1,1,2,2,3-pentachloropropane, the chlorinated compound is 1chloro-3,3,3-trifluoropropene and the tetrafluoropropene is2,3,3,3-tetrafluoropropene.
 13. The plant as claimed in claim 1,comprising: at least one first catalytic fluorination reactor; at leastone second catalytic fluorination reactor; a system for collecting astream of products connected at the outlet of the first catalyticfluorination reactor; a separation unit fed by the system for collectinga stream of products; a first collecting pipe and a second collectingpipe which are connected at the outlet of the separation unit, the firstcollecting pipe being configured in order to transport a streamcomprising hydrochloric acid and tetrafluoropropene and the secondcollecting pipe being configured in order to transport a streamcomprising hydrofluoric acid and chlorinated compound; an intermediatecollecting system connected at the outlet of the second reactor; a firstsystem for feeding with reaction medium configured in order to feed thefirst reactor, this being itself fed by the intermediate collectingsystem; a second system for feeding with reaction medium configured inorder to feed the second reactor, this being itself fed by the secondcollecting pipe; a system for feeding with regeneration streamconfigured in order to feed the first reactor and/or the second reactor;and a system for collecting a stream of gases stream resulting from theregeneration.
 14. The plant as claimed in claim 13, which comprises atleast two second reactors configured so that, when one of these reactorsis fed by the second system for feeding with reaction stream, the otherreactor is fed by the system for feeding with regeneration stream. 15.The plant as claimed in claim 13, which comprises at least two firstreactors and two second reactors configured so that, when one of thefirst reactors and one of the second reactors are respectively fed bythe first system for feeding with reaction stream and the second systemfor feeding with reaction stream, the other first reactor and the othersecond reactor are fed by the system for feeding with regenerationstream.
 16. The plant as claimed in claim 13, which comprises a singlesecond reactor configured in order to be fed sequentially either by thesecond system for feeding with reaction stream or by the system forfeeding with regeneration stream.
 17. The plant as claimed in claim 13,which comprises a single first reactor and a single second reactor,configured in order to be fed sequentially either by the second systemfor feeding with reaction stream or by the system for feeding withregeneration stream.
 18. A composition comprising tetrafluoropropene andcontaining, in molar proportions: less than 100 ppm of chloromethane;and/or less than 100 ppm of 1,1-difluoroethane; and/or less than 100 ppmof fluoromethane; and/or less than 100 ppm of difluoromethane.
 19. Thecomposition as claimed in claim 18, in which the tetrafluoropropene is2,3,3,3-tetrafluoropropene.
 20. The composition as claimed in claim 18,containing, in molar proportions: less than 50 ppm of chloromethane;and/or less than 50 ppm of 1,1-difluoroethane; and/or less than 50 ppmof fluoromethane; and/or less than 50 ppm of difluoromethane.